1. Field of the Invention
The present invention relates to a head-mounted display (HMD) and the optical engine thereof and more specifically to a head-mounted display capable of showing images formed by means of an LCoS (liquid crystal on silicon) device.
2. Description of the Related Art
In recent years, virtual reality, a type of computer simulation technology, has been vigorously developed, and can make wearers temporarily feel that they exist in the three-dimensional (3D) space of a simulated world. Through a head-mounted display, the imitative voices and images are sent directly to the sense organs of the wearer. Due to previous practical experiences, the wearer would really think of these imaginary imagines as real ones. Currently, such apparatus has been widely applied in computer games. If a space positioner and a 3D joystick are added to the apparatus, there would be feeling of truer reality.
In addition to being the standard apparatus of virtual reality, the head-mounted display may be used to further replace the display of a TV or a computer. Furthermore, it is also an optimal solution for privacy when one uses a notebook in public place to avoid peeping of the others. Also, many workers who constantly move about, for example, researchers, soldiers or stockjobbers, need to complete their works by wearing a head-mounted display.
In as early as the 1960s, a professor from the University of Utah, the USA, formed the first head-mounted display with a cathode ray tube monitor, an optical system intended for focusing, and a computerized image creation unit, wherein the process of displaying signals on the screen was controlled by means of rotation of head. Afterward, thin film transistor liquid crystal display (TFT-LCD) was applied to head-mounted displays, and thus head-mounted displays became lighter and have been used increasingly in fields like entertainment, medicine, education, etc.
Recently, the technology of miniaturized LCoS displays has forged into maturity, and the miniaturized LCoS displays have been applied to the image generator used in head-mounted displays. The principle of manufacturing LCoS displays is as follows: form an active matrix driving circuit for driving liquid crystal materials on silicon substrate with a CMOS manufacturing process, and stack a liquid crystal layer and a glass plate on the silicon substrate to form an LCoS display. A light source emits a ray that enters the liquid crystal layer through the glass plate and returns to the upper surface of the glass plate by reflection, and eventually the LCoS display reflects the predetermined image. Hence, LCoS displays are also known as reflective liquid crystal displays. Since LCoS displays have a relatively high aperture ratio, luminance, resolution and contrast, and the equipment for their manufacturing process is relatively common, LCoS displays will be the mainstream image generators for head-mounted displays.